Aidez moi pour cet exercice svp 20 points

Bonsoir,
A= 3/7 * 4/3 = 12/21 = 4/7
B= 2/7 *( -6/5) = -12/35
C= 1*4/7 = 4/7
D= 4/11 * -22/15 = -88/165 = -8/15